Field of the Invention
This invention relates to marking transfer sheets and particularly marking transfer sheets which are man and machine readable. More particularly, this invention relates to a process for marking an object using the marking transfer sheets.
Continuing effort has been directed toward the development of more satisfactory means for inventory control and supermarket checkout procedures. These efforts have resulted in a Universal Product Code (UPC), presented as an array of bars and spaces. Codes of this type are readable by a diffuse reflectance scanning means.
Despite the overall workability of this system, difficulty has been encountered in the development of a satisfactory means for applying the coded message. Traditional graphic art printing techniques, using two inks for the bars and the spaces, respectively, are limited by the tendency of the ink to spread during application. Moreover, the UPC system has minimum contrast requirements between the bar code and the background, since the coded information is read by detecting diffusely scattered light as reflected by the bars and the background. In addition, certain products and marking apparatus required the preparation of marks before application to the product. Accordingly, a continuing need exists for a reliable system for applying UPC code marks efficiently and accurately to a wide variety of substrates.
The present invention provides a marking transfer sheet particularly well suited for the application of marks such as UPC code labels, and a process for its use in applying such marks. These transfer sheets, when so used, result in the contrast required for this system independent of the reflective properties of the substrate, and provides a simplicity, precision and economy heretofore not available.